Player pianos have been in common usage for many years. While player pianos differ in their general configuration, they usually function in substantially the same manner.
A typical player piano has a keyboard containing 88 keys similar to the keys of most other pianos. Above the keyboard of most player pianos is a mechanism which provides for the automatic operation of the piano. This mechanism in most player pianos employs a tracker bar in which is situated an array of pneumatic holes. Each hole corresponds to a single key of the keyboard.
The typical player piano control apparatus also includes two spindles which cooperate to hold the ends of a scroll so the center of the scroll is stretched tightly across the tracker bar. The scroll, which is often called a tape, is usually made of paper.
The typical player piano utilizes a source of power and interior mechanical parts which wind the scroll from one spindle to the other across the tracker bar at a predetermined speed and which also include a pneumatic system that applies suction to each tracker bar hole on the side opposite the paper scroll. The pneumatic system detects a pressure differential in the tracker bar holes to operate the piano keyboard action in a predetermined manner.
The player piano action is controlled by putting openings of predetermined size and length in the paper scroll so the openings cross the tracker bar holes in a predetermined manner.
When a paper scroll hole is aligned with a tracker bar hole, the corresponding pneumatic system detects normal atmospheric pressure in the tracker bar hole. When a solid portion of the paper scroll covers a tracker bar hole, it prevents the passage of air through the tracker bar hole and the pneumatic mechanism therefore senses a different air pressure in the tracker bar hole than the level of air pressure existing therein when a hole in the paper scroll permits ambient air pressure surrounding the piano to communicate with the tracker bar hole.
The aforedescribed paper scroll and player piano mechanics in operation are attractive in a nostalgic sense, but have certain inherent disadvantages. For example, the paper scroll can easily be torn or damaged. The paper scroll is also relatively bulky. The scroll drive mechanism requires maintenance, and the paper roll may tear. Paper is also subject to distortion and warping from humidity changes and moisture content in the atmosphere. In addition, the whole paper drive process of winding the paper roll across a tracker bar involves a delivery apparatus especially vulnerable to mechanical failure from breakage and wear of parts, which generally include electric motor or vacuum drives, speed control governors, braking mechanisms, and tracking devices controlling paper alignment.
It is therefore an object of this invention to provide a process for reproducing key action of a piano by generating AC signals which are unique to the operation of each key, but unrelated to the musical instrument function performed by such key, recording such signals, reproducing such signals, and operating the keys corresponding to such signals.
It is a further object of this invention to provide a process of generating unique electric signals corresponding to key operation using only AC signals and in which the total energy responsive to each key operation is magnetically recorded at the same level to facilitate recording maximum data in a given recording medium.
It is a further object of this invention to provide apparatus for generating a recorded signal responsive to key operation by generating a recorded signal having combined components that are each of a discrete frequency and of equal energy levels in response to each key operation.
It is a further object of this invention to provide apparatus for reproducing key operation responsive to a recorded signal that includes multiple frequencies of equal energy by detecting each such recorded signal and operating a discrete unit in response to each frequency signal.
For purposes of describing the subject process, it should be noted that the term "key" may include any type apparatus having two discrete conditions. While the term "key" is primarily directed to those applications in which the key is one of a standard set of keys in a player piano, it will be apparent to persons versed in the art that for purposes of the subject process, a key may also be a key on an organ or a corresponding actuation mechanism on a different musical instrument and may also be a control unit on an instrument such as the sustain pedal on a piano or a stop on an organ which enhances particular sounds emanating from the organ. A key may also be an electric switch.